Materials handling vehicle path validation and dynamic path modification

ABSTRACT

A materials handling vehicle comprising a path validation tool and a drive unit, steering unit, localization module, and navigation module that cooperate to navigate the vehicle along a warehouse travel path. The tool comprises warehouse layout data, a proposed travel path, vehicle kinematics, and a dynamic vehicle boundary that approximates the vehicle physical periphery. The tool executes path validation logic to determine vehicle pose along the proposed travel path, update the dynamic vehicle boundary to account for changes in vehicle speed and steering angle, determine whether the dynamic vehicle boundary is likely to intersect obstacles represented in the layout data based on the determined vehicle pose at candidate positions along the proposed travel path, determine a degree of potential impingement at the candidate positions by referring to the dynamic vehicle boundary and obstacle data, and modify the proposed travel path to mitigate the degree of potential impingement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.Nos. 62/380,060 and 62/380,089, each filed Aug. 26, 2016.

BACKGROUND

The present disclosure relates to tools for verifying the path of amaterials handling vehicle, and more particularly, to path validationtools for verifying the path of a materials handling vehicle in awarehouse. For the purposes of defining and describing the concepts andscope of the present disclosure, it is noted that a “warehouse”encompasses any indoor or otherwise covered facility in which materialshandling vehicles transport goods including, but not limited to,warehouses intended primarily for the storage of goods, such as thosewhere multi-level warehouse racks are arranged in aisles, andmanufacturing facilities where goods are transported about the facilityby materials handling vehicles for use in one or more manufacturingprocesses.

BRIEF SUMMARY

According to the subject matter of the present disclosure, a materialshandling vehicle comprising a vehicle body, materials handling hardware,one or more wheels, a drive unit, a steering unit, a localizationmodule, a navigation module, and a path validation tool. The drive unit,steering unit, localization module, and navigation module cooperate todirect the materials handling vehicle along a travel path in awarehouse. The path validation tool comprises environmental layout dataof the warehouse, a proposed travel path within the warehouse,kinematics of the materials handling vehicle, and a dynamic vehicleboundary of the materials handling vehicle. The dynamic vehicle boundaryof the materials handling vehicle approximates the physical periphery ofthe materials handling vehicle. The path validation tool executes pathvalidation logic to (i) determine vehicle pose along the proposed travelpath, (ii) update the dynamic vehicle boundary to account for changes invehicle speed and steering angle, (iii) determine whether the dynamicvehicle boundary of the vehicle is likely to intersect obstaclesrepresented in the environmental layout data based on the determinedvehicle pose at candidate positions along the proposed travel path, (iv)determine a degree of potential impingement at the candidate positionsby referring to the dynamic vehicle boundary of the materials handlingvehicle and obstacle data represented in the environmental layout data,and (v) modify the proposed travel path to mitigate the degree ofpotential impingement. The drive unit, steering unit, localizationmodule, and navigation module cooperate to direct the materials handlingvehicle along the modified proposed travel path.

In embodiments, the dynamic vehicle boundary of the path validation toolcomprises a dynamic exterior boundary of the materials handling vehicleand a dynamic clearance boundary of the materials handling vehicle, andthe dynamic clearance boundary is enlarged relative to at least aportion of the dynamic exterior boundary of the materials handlingvehicle to define an enlarged boundary about at least a portion of thematerials handling vehicle. The path validation tool may execute pathvalidation logic to (i) determine whether the dynamic clearance boundaryof the materials handling vehicle is likely to intersect obstaclesrepresented in the environmental layout data based on the determinedvehicle pose at candidate positions along the proposed travel path, (ii)correlate likely points of intersection along the proposed travel pathwith vehicle pose at the candidate positions along the proposed travelpath to build a list of potentially intersecting candidates along theproposed travel path, and (iii) determine the degree of potentialimpingement at the candidate positions by referring to the list ofpotentially intersecting candidates, the dynamic exterior boundary ofthe materials handling vehicle, and obstacle data represented in theenvironmental layout data. The path validation tool may execute pathlogic to determine vehicle pose along one of the proposed travel pathand the modified proposed travel path at pre-determined intervals. Thekinematics of the material handling vehicle may comprise at least akinematic center C of the materials handling vehicle, data on thematerials handling vehicle to include exterior dimensions, a turningradius, and pose data.

The materials handling vehicle may comprise a tugger and one or moretrailers coupled to the tugger, and the pose data is indicative of posedata respectively of the tugger and the one or more trailers. Thematerials handling vehicle may comprise a tugger and one or moretrailers coupled to the tugger, the dynamic vehicle boundaryapproximates a physical periphery of the tugger of the materialshandling vehicle, and a potentially intersecting obstacle is a trailerof the one or more trailers coupled to the tugger. The materialshandling vehicle may comprise a tugger and one or more trailers coupledto the tugger, the dynamic vehicle boundary approximates a physicalperiphery of a trailer of the one or more trailers of the materialshandling vehicle, and a potentially intersecting obstacle is anothertrailer of the one or more trailers coupled to the trailer. Thematerials handling vehicle may comprise a tugger and one or moretrailers coupled to the tugger, the dynamic vehicle boundaryapproximates a physical periphery of one of the tugger and the one ormore trailers of the materials handling vehicle, and a potentiallyintersecting obstacle is an obstacle represented in the environmentallayout data separate from the materials handling vehicle.

In further embodiments, the path validation tool executes pathvalidation logic to (i) determine vehicle pose along the modifiedproposed travel path as the drive unit, steering unit, localizationmodule, and navigation module cooperate to direct the materials handlingvehicle along the modified proposed travel path, (ii) determine whetherthe dynamic vehicle boundary of the materials handling vehicle is likelyto intersect obstacles represented in the environmental layout databased on the determined vehicle pose at candidate positions along themodified proposed travel path, (iii) determine a degree of potentialimpingement at the candidate positions by referring to the dynamicvehicle boundary of the materials handling vehicle and obstacle datarepresented in the environmental layout data, (iv) dynamically modifythe modified proposed travel path to mitigate the degree of potentialimpingement and establish a dynamically modified travel path configuredto merge from and to the modified proposed travel path, and (v) navigatethe materials handling vehicle along the dynamically modified travelpath. Establishment of the dynamically modified travel path configuredto merge from and to the modified proposed travel path may comprisefitting a joining path to the modified proposed travel path, the joiningpath comprising a series of three clothoids and merge path lengths, themerge path lengths configured to be varied until a close fit comprisinga lowest join error is determined. Optimization towards the lowest joinerror may comprise an initial proposed merge path comprising a 1:1:1length ratio with respect to the ratios of clothoid lengths, the totallength of the initial proposed merge path, and a curvature at an end ofa first clothoid. The total length of the proposed merge path maycomprise a Euclidean distance between a pair of join points. Curvatureoptions with respect to the curvature may comprise an even spreadbetween a maximum allowed positive curvature and a maximum negative pathcurvature, the even spread based on one or more steer angle limits.

In embodiments, the path validation tool executes path validation logicto identify the degree of potential impingement at the candidatepositions as one or more problem areas of at least one of the proposedtravel path and a configuration of the materials handling vehicle withrespect to the proposed travel path. A degree of potential impingementmay comprise an impingement distance that is an overlap distance atcandidate positions indicative of an overlap between the dynamic vehicleboundary of the materials handling vehicle and obstacle data.

In accordance with one embodiment of the present disclosure, a materialshandling vehicle comprising a vehicle body, materials handling hardware,one or more wheels, a drive unit, a steering unit, a localizationmodule, a navigation module, and a path validation tool, wherein thedrive unit, steering unit, localization module, and navigation modulecooperate to direct the materials handling vehicle along a travel pathin a warehouse. The path validation tool comprises environmental layoutdata of the warehouse, a proposed travel path within the warehouse,kinematics of the materials handling vehicle, a dynamic exteriorboundary of the materials handling vehicle, and a dynamic clearanceboundary of the materials handling vehicle. The dynamic exteriorboundary of the materials handling vehicle approximates the physicalperiphery of the materials handling vehicle. The dynamic clearanceboundary is enlarged relative to at least a portion of the dynamicexterior boundary of the materials handling vehicle to define anenlarged boundary about at least a portion of the materials handlingvehicle. The path validation tool executes path validation logic to (i)determine vehicle pose along the proposed travel path, (ii) determinewhether the dynamic clearance boundary of the materials handling vehicleis likely to intersect obstacles represented in the environmental layoutdata based on the determined vehicle pose at candidate positions alongthe proposed travel path, (iii) correlate likely points of intersectionalong the proposed travel path with vehicle pose at the candidatepositions along the proposed travel path to build a list of potentiallyintersecting candidates along the proposed travel path, (iv) determine adegree of potential impingement at the candidate positions by referringto the list of potentially intersecting candidates, the dynamic exteriorboundary of the materials handling vehicle, and obstacle datarepresented in the environmental layout data, and (v) modify theproposed travel path to mitigate the degree of potential impingement.The drive unit, steering unit, localization module, and navigationmodule cooperate to direct the materials handling vehicle along themodified proposed travel path.

In embodiments, the path validation tool executes path validation logicto update the dynamic exterior boundary and the dynamic clearanceboundary to account for changes in vehicle speed and steering angle. Adegree of potential impingement may comprise an impingement distancethat is an overlap distance between a potentially intersecting candidateand the dynamic exterior boundary. The materials handling vehicle maycomprise a tugger and one or more trailers coupled to the tugger, andthe potentially intersecting candidate is one of the tugger, a trailer,and an obstacle represented by obstacle data in the environmental layoutdata. The potentially intersecting candidate may be a trailer, and theoverlap distance is defined between the trailer and the dynamic exteriorboundary of the tugger of the materials handling vehicle. Thepotentially intersecting candidate may be a trailer, and the overlapdistance is defined between the trailer and the dynamic exteriorboundary of another trailer of the one or more trailers of the materialshandling vehicle. The potentially intersecting candidate may be theobstacle, and the overlap distance is defined between the obstacle andthe dynamic exterior boundary of the materials handling vehicle.

In accordance with another embodiment of the present disclosure is amethod of executing path validation logic with respect to a materialshandling vehicle comprising a vehicle body, materials handling hardware,one or more wheels, a drive unit, a steering unit, a localizationmodule, a navigation module, and a path validation tool, the drive unit,steering unit, localization module, and navigation module cooperate todirect the materials handling vehicle along a travel path in awarehouse, the method comprising receiving a plurality of inputs intothe path validation tool, the plurality of inputs comprisingenvironmental layout data of the warehouse, a proposed travel pathwithin the warehouse, kinematics of the materials handling vehicle, anda dynamic vehicle boundary of the materials handling vehicle thatapproximates the physical periphery of the materials handling vehicle.The method further comprises determining vehicle pose along the proposedtravel path through the path validation tool, updating the dynamicvehicle boundary to account for changes in vehicle speed and steeringangle through the path validation tool, determining whether the dynamicvehicle boundary of the vehicle is likely to intersect obstaclesrepresented in the environmental layout data based on the determinedvehicle pose at candidate positions along the proposed travel paththrough the path validation tool, determining a degree of potentialimpingement at the candidate positions by referring to the dynamicvehicle boundary of the materials handling vehicle and obstacle datarepresented in the environmental layout data through the path validationtool, modifying the proposed travel path to mitigate the degree ofpotential impingement through the path validation tool, and navigatingthe materials handling vehicle along the modified proposed travel paththrough cooperation of the drive unit, steering unit, localizationmodule, and navigation module.

In accordance with yet another embodiment of the present disclosure is amethod of executing path validation logic with respect to a materialshandling vehicle comprising a vehicle body, materials handling hardware,one or more wheels, a drive unit, a steering unit, a localizationmodule, a navigation module, and a path validation tool, the drive unit,steering unit, localization module, and navigation module cooperate todirect the materials handling vehicle along a travel path in awarehouse, the method comprising receiving a plurality of inputs intothe path validation tool, the plurality of inputs comprisingenvironmental layout data of the warehouse, a proposed travel pathwithin the warehouse, kinematics of the materials handling vehicle, adynamic exterior boundary of the materials handling vehicle, and adynamic clearance boundary of the materials handling vehicle. Thedynamic exterior boundary of the materials handling vehicle approximatesthe physical periphery of the materials handling vehicle. The dynamicclearance boundary is enlarged relative to at least a portion of thedynamic exterior boundary of the materials handling vehicle to define anenlarged boundary about at least a portion of the materials handlingvehicle. The method further comprises determining vehicle pose along theproposed travel path through the path validation tool, determiningwhether the dynamic clearance boundary of the materials handling vehicleis likely to intersect obstacles represented in the environmental layoutdata based on the determined vehicle pose at candidate positions alongthe proposed travel path through the path validation tool, correlatinglikely points of intersection along the proposed travel path withvehicle pose at the candidate positions along the proposed travel pathto build a list of potentially intersecting candidates along theproposed travel path through the path validation tool, determining adegree of potential impingement at the candidate positions by referringto the list of potentially intersecting candidates, the dynamic exteriorboundary of the materials handling vehicle, and obstacle datarepresented in the environmental layout data through the path validationtool, modifying the proposed travel path to mitigate the degree ofpotential impingement through the path validation tool, and navigatingthe materials handling vehicle along the modified proposed travel paththrough cooperation of the drive unit, steering unit, localizationmodule, and navigation module.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and notintended to limit the subject matter defined by the claims. Thefollowing detailed description of the illustrative embodiments can beunderstood when read in conjunction with the following drawings, wherelike structure is indicated with like reference numerals and in which:

FIGS. 1, 1A, and 1B depict a top view of a materials handling vehicleaccording to one or more embodiments shown and described herein;

FIG. 1C depicts a top view of another materials handling vehicleaccording to one or more embodiments shown and described herein;

FIG. 1D depicts a side view of the materials handling vehicle of FIG.1C;

FIG. 2 depicts a top view of another embodiment of the materialshandling vehicle according to one or more embodiments shown anddescribed herein;

FIG. 3 depicts a computing environment according to one or moreembodiments shown and described herein;

FIG. 4 depicts a tugger according to one or more embodiments shown anddescribed herein;

FIG. 5 depicts a trailer according to one or more embodiments shown anddescribed herein;

FIG. 6 depicts another embodiment of the trailer according to one ormore embodiments shown and described herein;

FIG. 7 depicts another embodiment of the trailer according to one ormore embodiments shown and described herein;

FIG. 8 depicts a tugger and a trailer according to one or moreembodiments shown and described herein;

FIG. 9 depicts another embodiment of the tugger and trailer according toone or more embodiments shown and described herein;

FIG. 10 depicts another embodiment of the tugger and one or moretrailers according to one or more embodiments shown and describedherein;

FIG. 11 depicts intersection calculations along a path in a warehouseaccording to one or more embodiments shown and described herein;

FIG. 12 depicts one or more steps to verify a path according to one ormore embodiments shown and described herein;

FIG. 13 depicts a process to update a dynamic vehicle boundary accordingto one or more embodiments shown and described herein;

FIG. 14 depict a path modification process to mitigate a degree ofimpingement based on a dynamic clearance boundary and a dynamic exteriorboundary according to one or more embodiments shown and describedherein;

FIG. 15 depicts a materials handling vehicle including a dynamic vehicleboundary around a tugger and a plurality of trailers and disposed on apath according to one or more embodiments shown and described herein;

FIG. 16 depicts a materials handling vehicle on a dynamically translatedpath from a nominal path according to one or more embodiments shown anddescribed herein;

FIG. 17 depicts a process for path optimization of a materials handlingvehicle according to one or more embodiments shown and described herein;and

FIG. 18 graphically depicts results of changes made to a path to avoidan obstacle according to one or more embodiments shown and describedherein.

DETAILED DESCRIPTION

The following text sets forth a broad description of numerous differentembodiments of the present disclosure. The description is to beconstrued as exemplary only and does not describe every possibleembodiment since describing every possible embodiment would beimpractical, if not impossible, and it will be understood that anyfeature, characteristic, component, composition, ingredient, product,step or methodology described herein can be deleted, combined with orsubstituted for, in whole or part, any other feature, characteristic,component, step or methodology described herein. It should be understoodthat multiple combinations of the embodiments described and shown arecontemplated and that a particular focus on one embodiment does notpreclude its inclusion in a combination of other described embodiments.Numerous alternative embodiments could also be implemented, using eithercurrent technology or technology developed after the filing date of thispatent, which would still fall within the scope of the claims.

Referring to FIGS. 1-1D, a materials handling vehicle 10, 10′ is showncomprising a vehicle body 11, materials handling hardware 15, 15′, oneor more wheels 16, a drive unit D, a steering unit S, a localizationmodule L, a navigation module N, and a path validation tool P. At leastone wheel 16 may be part of the steering unit S. FIGS. 1C-1D illustratea materials handling vehicle 10′ in the form of a lift truck comprisingconventional materials handling vehicle hardware, such as a steeringunit S, a localization module L, a navigation module N, materialshandling hardware 15′, and a drive unit D, the details of which arebeyond the scope of the present disclosure and may be gleaned fromconventional and yet-to-be developed teachings in the materials handlingvehicle literature—examples of which include U.S. Pat. Nos. 6,135,694,RE37215, 7,017,689, 7,681,963, 8,131,422, and 8,718,860, each of whichis assigned to Crown Equipment Corporation.

Referring to FIG. 1D, the materials handling vehicle 10′ may include oneor more user interfaces that permit an operator to interface with thecontrol functions of the materials handling vehicle. For example, andnot by way of limitation, suitable user interfaces include, but are notlimited to, conventional or yet-to-be developed operator compartmentcontrol devices, such as hand-operated control device 43 for controllingthe materials handling hardware 15′, a foot-operated vehicle speedcontrol device 45 operatively coupled to the vehicle drive mechanism, atouch screen hardware control interface, which may be integral to, orseparate from, an operator compartment display device 47, a steeringcontrol device 44 operatively coupled to the steered wheels of thematerials handling vehicle 10, or combinations thereof. The materialshandling hardware 15′ may be any type of conventional or yet-to-bedeveloped hardware equipped to handle materials, is typically configuredto facilitate the storage and retrieval of goods, and may include, butis not limited to, a set of fork tines, a container handler, a turretwith forks, a pantrograph, a telescopic handler, and the like.

In one embodiment, the user interface may comprise an antenna 42 orother type of automated interface with an external or remote controldevice, which may be used to issue commands to the materials handlingvehicle 10′ or otherwise remotely control the materials handling vehicle10′. The antenna 42 can be configured to wirelessly communicativelycouple the materials handling vehicle 10′ to a remote computer.Alternatively, or additionally, other types of automated interfaces maybe provided, such as, for example, input/output ports, such as RS-232connectors, USB ports, or the like. These types of interfaces may beprovided to facilitate a hard wired connected between the materialshandling vehicle 10′ and a remote computer such as a laptop.

In the embodiment illustrated in FIG. 1, the materials handling hardware15 comprises storage and retrieval hardware in the form of verticallydisplaceable and articulating forks, and one or more wheels 16, at leastone of which is steerable and, as such, part of the steering unit. It iscontemplated that, although the drive unit D, steering unit S,localization module L, navigation module N, and a path validation tool Pare illustrated schematically as separate components of the materialshandling vehicle, these components may be configured in a variety ofways, either as fully independent units, or as units that partially orfully share hardware and/or software.

Referring collectively to FIGS. 1, 1A, and 1B, the physical periphery ofthe materials handling vehicle 10 may be approximated by two differenttypes of dynamic vehicle boundaries: a dynamic exterior boundary 13 anda dynamic clearance boundary 19. As is described in further detailherein, the dynamic exterior boundary 13 is a relatively closeapproximation of the physical periphery of the vehicle and may, forexample, be represented by a simple or irregular polygon, by a shapeconsisting of a combination of curved and linear portions, or by acomplex, non-geometric shape, each of which are designed to approximatethe footprint of the vehicle. Although the dynamic exterior boundary 13may be defined at any offset distance d from the physical periphery ofthe materials handling vehicle 10, it is contemplated that the offsetwill be relatively close to the body 11 of the vehicle 10, and, like thephysical periphery, may vary from vehicle to vehicle depending upon avariety of factors. FIGS. 1A and 1B illustrate the dynamic clearanceboundary 19, which is offset from the dynamic exterior boundary 13 ofthe vehicle by a distance d′ that may be generally uniform, e.g., 0.5 m.Although the dynamic exterior boundary 13 and the dynamic clearanceboundary 19 are illustrated in FIGS. 1, 1A, and 1B as being offset fromthe physical periphery of the vehicle 10 in a fairly uniform manner, itis contemplated that these boundaries may be offset from the physicalperiphery of the vehicle to different degrees, along different portionsof the physical periphery. For example, it may be advantageous toincorporate a significantly larger boundary offset on a forward-facingside of the vehicle, as compared to a rearward-facing side of thevehicle. Regardless, the respective roles, and dynamic nature of, thedynamic exterior boundary 13 and the dynamic clearance boundary 19, aredescribed in further detail below.

It is noted that many materials handling vehicles 10 will includehardware that articulates, or otherwise moves, to change the footprintof the vehicle. Referring to FIG. 1, examples of such hardware include,for example, vehicle forks or other storage and retrieval hardware 15that can extend and/or rotate, operator compartment doors that open andclose, robotic arms, etc. To account for this, as is illustrated in FIG.1, the dynamic exterior boundary 13 may also include portions thatapproximate any articulation boundaries 17 of the vehicle.

Although the dynamic exterior boundary 13 is illustrated in FIG. 1 as arelatively a complex shape consisting of a combination of curved andlinear portions, it is contemplated that, in many cases, it will beadvantageous to present the dynamic exterior boundary as an irregularpolygon by eliminating the curved portions. By doing so, thosepracticing the concepts of the present disclosure will still have a moreaccurate representation of the peripheral outline of the vehicle, whencompared to a simple rectangular boundary, but will enjoy asignificantly reduced computational load, when compared to the complexshape of FIG. 1. FIG. 1A presents an example of a dynamic exteriorboundary 13 in the form of an irregular polygon, without the use of thecurved boundary portions of FIG. 1. FIG. 1B presents an example of anexpanded dynamic exterior boundary 13 in the form of an irregularpolygon, without the use of the curved boundary portions of FIG. 1.

FIG. 2 depicts another embodiment of the materials handling vehicle 10comprising the body 11, the aforementioned drive unit D, steering unitS, localization module L, navigation module N, and path validation toolP, one or more wheels 16, at least one of which is steerable and part ofthe steering unit, and a coupling device 18. In the embodimentillustrated in FIG. 2, materials handling hardware may be provided onthe vehicle body 11 or may be provided as materials carrying surfaces orengagement hardware on one or more trailers connected via the couplingdevice 18, which may be a hitch, a hook, a pintle hook, lunette eye, aball hitch, and like types of towing couplers. It should be understoodthat although embodiments of the materials handling vehicle 10, 10′ areshown in FIGS. 1-2, any type of materials handling vehicle including,for example, forklifts, lift trucks, tractors, tugger-trailer trains,etc.; including, but not limited to, those powered materials handlingvehicles identified by the United States Department of Labor,Occupational Safety & Health Administration (OSHA) in Class I—ElectricMotor Rider Trucks, Class II—Electric Motor Narrow Aisle Trucks, ClassIII—Electric Motor Hand Trucks or Hand/Rider Trucks, Class IV—InternalCombustion Engine Trucks (Solid/Cushion Tires), Class V—InternalCombustion Engine Trucks (Pneumatic Tires), Class VI—Electric andInternal Combustion Engine Tractors, and Class VII—Rough TerrainForklift Trucks.

Note that FIG. 3 and the associated discussions provide a brief, generaldescription of a suitable computing environment in which the presentdisclosure can be implemented. Although not required, aspects of thesoftware are described in the general context of computer-executableinstructions, such as routines executed by a general-purpose computer,e.g., stationary and mobile computers. Those skilled in the relevant artwill appreciate that the software can be practiced with othercommunications, data processing, or computer system configurations,including: Internet appliances, handheld devices (including personaldigital assistants (PDAs)), wearable computers, all manner of cellularor mobile phones, multi-processor systems, microprocessor-based orprogrammable consumer electronics, set-top boxes, network PCs,mini-computers, mainframe computers, server computers, and the like.Indeed, the terms “computer” and the like are generally usedinterchangeably herein, and refer to any of the above devices andsystems, as well as any data processor. Aspects of the software can beembodied in a special purpose computer or data processor that isspecifically programmed, configured, or constructed to perform one ormore of the computer-executable instructions explained in detail herein.Aspects of the software can also be practiced in distributed computingenvironments where tasks or modules are performed by remote processingdevices, which are linked through a communications network, such as aLocal Area Network (LAN), Wide Area Network (WAN), or the Internet. In adistributed computing environment, program modules may be located inboth local and remote memory storage devices. Indeed, computerimplemented instructions, data structures, screen displays, and otherdata under aspects of the software may be distributed over the Internetor over other networks (including wireless networks), on a propagatedsignal on a propagation medium (e.g., an electromagnetic wave(s), asound wave, etc.) over a period of time, or they may be provided on anyanalog or digital network (packet switched, circuit switched, or otherscheme).

The path validation tool P may be embodied in hardware and/or insoftware (including firmware, resident software, micro-code, etc.). Inone embodiment, the path validation tool P is embodied in software andhardware. For example, referring to FIG. 3, the path validation tool Pmay comprise a program embodied in a computing device 200, which maycomprise a vehicle controller including at least one processor 205, anda computer-readable medium 210 communicatively coupled through a localinterface 215. Alternatively, suitable path validation tool software maybe stored in a computer-useable or computer-readable medium 210accessible by the vehicle controller (e.g., over a network). Acomputer-usable or the computer-readable medium 210 may be anynon-transitory medium that can contain, store, communicate, propagate,or transport software for use by or in connection with the computingdevice 200.

The computer-usable or computer-readable medium 210 may be, for examplebut not limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, device, or propagationmedium. More specific examples (a non-exhaustive list) of thecomputer-usable or computer-readable medium 210 would include thefollowing volatile and non-volatile examples: an electrical connectionhaving one or more wires, a computer diskette, a random access memory(RAM) (including SRAM, DRAM, and/or other types of RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM or Flashmemory), secure digital (SD) memory, registers, one or more opticalfibers, a compact disc read-only memory (CD-ROM), and/or a digital videodisc read-only memory (DVD-ROM). Note that the computer-usable orcomputer-readable medium 210 could even be paper or another suitablemedium upon which the program is printed, as the program can beelectronically captured, via, for instance, optical scanning of thepaper or other medium, then compiled, interpreted, or otherwiseprocessed in a suitable manner, if necessary, and then stored in acomputer memory. In other words, non-transitory computer-usable orcomputer-readable medium 210 may include those computer-usablecomputer-readable mediums that are not signals per se. Depending on theparticular embodiment, these non-transitory computer-usablecomputer-readable mediums may reside within the computing device 200and/or external to the computing device 200.

Computer program code for carrying out the path validation tool of thepresent disclosure may be written in a high-level programming language,such as C or C++, for development convenience. In addition, computerprogram code for carrying out the path validation tool of the presentdisclosure may also be written in other programming languages, such as,but not limited to, interpreted languages. Some modules or routines maybe written in assembly language or even micro-code to enhanceperformance and/or memory usage. However, software embodiments of thepresent disclosure do not depend on implementation with a particularprogramming language. It will be further appreciated that thefunctionality of any or all of the program modules may also beimplemented using discrete hardware components, one or more applicationspecific integrated circuits (ASICs), or a programmed digital signalprocessor, or microcontroller.

Additionally, the computer-usable or computer-readable medium 210 may beconfigured to store operating logic 230 and executable logic 235. Theoperating logic 230 may include an operating system, basic input outputsystem (BIOS), and/or other hardware, software, and/or firmware foroperating the computing device 200. The executable logic 235 comprisesthe path validation logic 240 which may each comprise a plurality ofdifferent pieces of logic, each of which may be embodied, as anon-limiting example, as a computer program, firmware, and/or hardware.The local interface 215 may comprise as a bus or other communicationinterface to facilitate communication among the components of thecomputing device 200.

The processor 205 may include any processing component operable toreceive and execute instructions (such as from the data storage 245and/or computer-readable medium 210). The input/output hardware 220 mayinclude and/or be configured to interface with a monitor, positioningsystem, keyboard, mouse, printer, image capture device, microphone,speaker, sensors, gyroscope, compass, and/or other device for receiving,sending, and/or presenting data. The network interface hardware 225 mayinclude and/or be configured for communicating with any wired orwireless networking hardware, including an antenna, a modem, LAN port,wireless fidelity (Wi-Fi) card, WiMax card, mobile communicationshardware, and/or other hardware for communicating with other networksand/or devices. From this connection, communication may be facilitatedbetween the computing device 200 and other computing devices. In oneembodiment, the processor 205 may include and/or be coupled to agraphical processing unit (GPU).

The computing device 200 may comprise data storage 245. Data storage maybe a subset of the computer-usable or computer-readable medium 210 or itmay be a separate and distinct component within the computing device200. The data storage 245 may comprise one or more data sets for use bythe operating logic 230 and/or the executable logic 235. The data setsmay comprise configuration data 250, environmental data 255, and vehicledata 260.

It should be understood that the components illustrated in FIG. 3 aremerely exemplary and are not intended to limit the scope of thisdisclosure. As a non-limiting example, while the components in FIG. 3are illustrated as residing within the computing device 200, this ismerely an example and in some embodiments, one or more of the componentsmay reside external to the computing device 200. It should also beunderstood that, while the computing device 200 is illustrated as asingle device, this is also merely an example and in some embodiments,the path validation logic 240 may reside on different devices.Additionally, while the computing device 200 is illustrated with thepath validation logic 240 as a single piece of logic, in someembodiments, the path validation logic 240 may comprise two or moreseparate logical components to perform the described functionality.

FIG. 4 depicts a tugger 20 as one embodiment of a materials handlingvehicle. The tugger 20 may comprise a tugger body 25, one or moresteered wheels 22, one or more fixed wheels 24, and the coupling device18. FIG. 4 also shows the dynamic exterior boundary 13 of the tugger 20.This dynamic exterior boundary 13 may be a simple polygon, asillustrated in FIG. 4, or may be a more complex shape that more closelyfollows the physical periphery of the tugger body 25, i.e., it mayinclude the projections of hardware mounted to the tugger body 25 suchas racks, equipment, attachment points, and the like, or include one ormore articulation boundaries like the one shown in FIG. 1. For example,and not by way of limitation, the dynamic exterior boundary 13 may berepresented by a polygon such as a box, square, circle, trapezoid,triangle, and the like. FIG. 4 illustrates an embodiment where thedynamic exterior boundary 13 is a rectangle that encapsulates the tuggerbody 25 and any projections of hardware mounted to the tugger body 25such as racks, equipment, attachment points, articulation boundaries,and the like. The coupling device 18 removably couples with a tuggercoupling device 26 (FIG. 5) of a trailer 50, which is shown in FIG. 5.Collectively, the tugger 20 and trailer 50 form a materials handlingvehicle.

Characteristic specific to the tugger 20 may be identified and recordedin the vehicle data 260 (FIG. 3) for use by the path validation tool.Referring to FIG. 4, the vehicle data may comprise tugger type,wheel_type (e.g., quantity and location of steered wheels 22 and fixedwheels 24), wheelbase dimensions between the one or more wheels of thetugger 20 (e.g., the dimensions between the steered wheel 22 and thefixed wheels 24), rear_hitch dimensions, a kinematic center C of thetugger 20, and the like. It is noted that the rear_hitch dimensionsinclude a distance D_(rear_hitch) measured from the distal end 23 of thecoupling device 18 to the kinematic center C. Configuration data 250(FIG. 3) may comprise data representing clearance boundary data whichmay be an offset distance from the dynamic exterior boundary 13 of thetugger 20.

Referring to FIG. 5, one embodiment of a trailer 50 is shown,specifically, a caster steer trailer which comprises one or more fixedwheels 24, one or more caster wheels 27, and one or more tugger couplingdevices 26. Characteristic of the trailer 50 may comprise trailer type(e.g., caster steer trailer), wheel_type (e.g., quantity and location ofcaster wheels 27 and fixed wheels 24), wheelbase dimensions between theone or more wheels of the trailer 50 (e.g., the dimensions between thecaster wheels 27 and the fixed wheels 24), rear_hitch dimensions,front_hitch dimensions, a kinematic center C of the trailer 50, and thelike. It is noted that the rear_hitch dimensions include a distanceD_(rear_hitch) measured from the distal end 23 of the rear tuggercoupling device 26 a to the kinematic center C, and the front_hitchdimensions include a distance D_(front_hitch) measured from the distalend 23 of the front trailer coupling device 26 b to the kinematic centerC. Configuration data 250 (FIG. 3) may comprise data representing adynamic clearance boundary which may be an offset distance from thedynamic exterior boundary 13 of the trailer 50.

FIG. 6 is one embodiment of the trailer 50, specifically a two-wheelsteer trailer which comprises one or more fixed wheels 24, one or moresteered wheels 22, a tugger coupling device 26, and a steered couplingdevice 28. Characteristic of the trailer 50 may comprise trailer type(e.g., two-wheel steer trailer), wheel_type (e.g., quantity and locationof steered wheels 22 and fixed wheels 24), wheelbase dimensions betweenthe one or more wheels of the trailer 50 (e.g., the dimensions betweenthe steered wheels 22 and the fixed wheels 24), rear_hitch dimensions,front_hitch dimensions, a kinematic center C of the trailer 50, amax_steer angle (θ_(steer_max)) of the steered coupling device 28, andthe like. It is noted that the rear_hitch dimensions include a distanceD_(rear_hitch) measured from the distal end 23 of the rear tuggercoupling device 26 a to the kinematic center C, and the front_hitchdimensions include a distance D_(front_hitch) measured from the distalend 23 of the steered coupling device 28 to the steered pivot point 29.The max_steer angle is measured in relation of rotation of the distalend 23 of the steered coupling device 28 around a steered pivot point29. Configuration data 250 (FIG. 3) may comprise clearance polygon datawhich may be an offset distance from the dynamic exterior boundary 13 ofthe trailer 50.

FIG. 7 is one embodiment of the trailer 50, specifically a four-wheelsteer trailer which comprises one or more steered wheels 22, a tuggercoupling device 26, and a steered coupling device 28. Characteristic ofthe trailer 50 may comprise trailer type (e.g., four-wheel steertrailer), wheel_type (e.g., quantity and location of steered wheels 22),wheelbase dimensions between the one or more wheels of the trailer 50(e.g., half the distance between the steered wheels 22), rear_hitchdimensions, front_hitch dimensions, a kinematic center C of the trailer50, a max_steer angle of the steered coupling device 28, and the like.It is noted that the rear_hitch dimensions are measured from the distalend 23 of the rear tugger coupling device 26 a to the kinematic center Cand the front_hitch dimensions are measured from the distal end 23 ofthe steered coupling device 28 to the steered pivot point 29. Themax_steer angle is measured in relation of rotation of the distal end 23of the steered coupling device 28 around a steered pivot point 29.Configuration data 250 (FIG. 3) may comprise data representing thedynamic exterior boundary and the dynamic clearance boundary, both ofwhich are offset from the physical periphery of the trailer 50.

Referring to back to FIG. 3, the path validation tool models a materialshandling vehicle and one or more trailers to define the motion of thematerials handling vehicle and one or more trailers around a path in awarehouse. The path validation tool predicts the position of thematerials handling vehicle and one or more trailers, if coupled to thematerials handling vehicle, at any point along the path in thewarehouse. The materials handling vehicle, including each trailer, isdefined by a dynamic exterior boundary 13 (FIGS. 4-7) along with itskinematic center C (FIGS. 4-7), by the path validation logic 240, and bythe data stored in the data storage 245. The path validation tooldetermines the pose (i.e., orientation, position and heading) of thematerials handling vehicle, including one or more trailers, in relationto the path at regular, pre-determined intervals (i.e., at every fixeddistance interval along the path) and identifies if there are anyprojected intersections between each trailer, between the trailers andthe materials handling vehicle, and/or between the materials handlingvehicle and any obstacles in the warehouse. For example, and not by wayof limitation, the path validation tool may calculate the pose of thematerials handling vehicle, including trailers, along the path at every5 cm of travel distance along the path. Further, in embodiments, thematerials handling vehicle 10 may include a tugger 20 and one or moretrailers 50 coupled to the tugger 20. The dynamic vehicle boundary mayapproximate a physical periphery of the tugger 20 of the materialshandling vehicle 10, and a potentially intersecting obstacle is atrailer 50 of the one or more trailers 50 coupled to the tugger 20.Alternatively, the dynamic vehicle boundary may approximate a physicalperiphery of a trailer 50 of the one or more trailers 50 of thematerials handling vehicle 10, and a potentially intersecting obstacleis another trailer 50 of the one or more trailers 50 coupled to thetrailer 50. In another embodiment, the dynamic vehicle boundary mayapproximate a physical periphery of one of the tugger 20 and the one ormore trailers 50 of the materials handling vehicle 10, and a potentiallyintersecting obstacle is an obstacle represented in the environmentallayout data separate from the materials handling vehicle.

For each fixed distance interval along the path, the pose of thematerials handling vehicle, including each trailer, if coupled to thematerials handling vehicle, is calculated from the prior state or theprior pose at the prior fixed distance interval along the path. For eachpose of materials handling vehicle 10 and one or more trailers 50, theirrespective exterior and clearance polygons are calculated for that poseand checked for intersection with any obstacle in a quad tree. Obstacleobservations will be maintained in a quad tree to allow high efficiencyspatial queries, with bounds large enough to cover the entire path plusthe range of the laser scanner including its positional offset. The quadtree is able to contain obstacles in the form of points and lines, orany other necessary form. The quad tree provides high efficiency lookupof nearby obstacles for intersection checks. The quad tree returns ashortlist of potentially intersecting candidates, greatly reducing thenumber of intersection checks. It is noted that quadtree-based spatialqueries are well documented in the art and it is contemplated that avariety of different quadtree configurations may be implemented withinthe scope of the present disclosure.

Each polygon (such as a dynamic vehicle boundary illustrated in FIG. 1)for the materials handling vehicle, and all connected trailers, ischecked for intersection (i.e., collision, or intrusion) with anotherpolygon or obstacle in the warehouse. This allows early exit if anintersection is found and return or output of the failure condition. Ifan intersection is found, the path validation tool will provide theposition along the path, the materials handling vehicle, trailer, and/orobstacle affected by the intersection, and an impingement distance. Theimpingement distance is an overlap distance of two or more polygonsand/or one or more polygons with one or more obstacles and may be usedto modify or revise the path to avoid the obstacle or used to modify theturn radius or hitch length of each trailer to avoid pinching betweentrailers or between the trailer and materials handling vehicle. Thus, adegree of potential impingement may include an impingement distance thatis an overlap distance at candidate positions indicative of an overlapbetween the dynamic vehicle boundary of the materials handling vehicleand obstacle data. Any obstacle that intersects any clearance polygon,or the materials handling vehicle and trailers' swept paths will need tobe checked for its distance along the path and its impingement distance.This will allow feedback for path modification and notification ofhazard zones. The swept path is the area covered by any part of thetugger and trailers as it follows the path and is the combination of alltugger and trailer polygons at all steps along the path.

Referring to FIGS. 1A-1B, two polygons will be used for each calculationat each fixed distance d along the path: (i) a dynamic exterior boundary13 polygon offset a distance d from the physical periphery of thevehicle and (ii) a dynamic clearance boundary 19 polygon that isexpanded relative to the dynamic exterior boundary 13 by an offsetdistance d′ of, for example, 0.5 meters, or whatever distance issuitable in practice. In an embodiment in which the overall dynamicclearance boundary 19 is greater than the overall dynamic exteriorboundary 13, each calculation by the path validation tool at each fixeddistance interval may use the clearance polygon first. If anintersection is not identified with the dynamic clearance boundary, thena second calculation using the dynamic exterior boundary is not done.

The dynamic exterior boundary 13 may be a polygon that contains thephysical extents of all active scan fields, which are configured tomatch the fields contained on one or more sensors coupled to thematerials handling vehicle 10. For example, the one or more sensors mayinclude a camera, 3D camera (e.g., Time of Flight), 2D and/or 3D laserscanners, radar array, ultrasonic array, or other scan system devicesconfigured to generate an active scan field such that an obstacleimpinging on the active scan field will cause the vehicle to stop. Ascan system as described herein may refer to a device onboard thematerials handling vehicle 10 that is configured to quickly and reliablyhalt the materials handling vehicle 10 if any active scan field containsan obstacle. The device may select the active scan field from a list ofpotential scan fields based on a speed and steering angle of thematerials handling vehicle 10. An active scan field as referenced hereinmay be a physical area relative to the industrial vehicle that ismonitored by the scan system for a given speed and steering angle of thematerials handling vehicle 10. A dynamic exterior boundary 13 asdescribed herein may refer to a dynamic shape that contains a physicaloutline of the materials handling vehicle 10 in addition to any activescan fields and may include a slightly larger dimension to provide for amargin for error. For example, in one embodiment, referring to FIG. 11,there may an active scan field 38 projected from a leading edge of thematerials handling vehicle 10 that is configured to identify one or moreobstacles in front of or lateral to the materials handling vehicle 10along a physically swept area 39 disposed around a travel path 37. Thephysically swept area 39 may be sufficiently wide to encompass a widthof the materials handling vehicle 10 along with variations of the travelpath 37 that occur in response to obstacle detection. In embodiments,the dynamic exterior boundary 13 and/or the travel path 37 may begenerated or modified based on obstacle(s) identified by at least theactive scan field 38.

The dynamic clearance boundary 19 may be a polygon generated withrespect to a periphery of the materials handling vehicle 13. A dynamicclearance boundary 19 as described herein may refer to a dynamic shapethat contains a physical outline of the materials handling vehicle 10 inaddition to an expansion area defined by a constant clearance distanceand may also include a slightly larger dimension to provide for a marginfor error. In embodiments, the dynamic clearance boundary 19 may beimpinged in a hazard zone such that the vehicle is permitted to continueto be navigated as long as the dynamic exterior boundary 13 is notimpinged. Further, in embodiments, portions of the dynamic exteriorboundary 13 may be larger than portions of the dynamic clearanceboundary 19. For example, one or more portions of the dynamic exteriorboundary 13 may be larger than portions of the dynamic clearanceboundary 19, while other portions of the dynamic exterior boundary 13may be smaller than portions of the dynamic clearance boundary 19. Inembodiments in which portions of the dynamic exterior boundary 13 may begreater than the dynamic clearance boundary 19, each calculation by thepath validation tool at each fixed distance interval may use both theclearance polygon and the exterior polygon. For example, a left sideportion of the vehicle may have a dynamic exterior boundary 13 that islarger than the dynamic clearance boundary 19, and a right side portionof the vehicle may have a dynamic exterior boundary 13 that is smallerthan the dynamic clearance boundary 19. Whenever an intersection orimpingement is found with respect to the dynamic exterior boundary 13 atany portion, the vehicle will stop. Further, while in some instances thevehicle may stop or execute obstacle avoidance when an intersection isfound for a portion of the dynamic clearance boundary 19 but not thedynamic exterior boundary 13, the vehicle may in other instancescontinue with navigation if the vehicle is in a hazard zone when theintersection of the portion of the dynamic clearance boundary 19 isidentified. Thus, as a non-limiting example, an intersection may not beidentified for the left side portion of the vehicle having the dynamicexterior boundary 13 that is larger than the dynamic clearance boundary19, while an intersection may be identified for the dynamic clearanceboundary 19 of the right side portion of the vehicle having a dynamicexterior boundary 13 that is smaller than the dynamic clearance boundary19 (but not identified for the dynamic exterior boundary 13). In such adetected situation, obstacle avoidance may occur. However, if thevehicle is in a hazard zone during this detected situation, the obstaclescanning tool may not employ obstacle avoidance and the vehicle maycontinue with navigation along the travel path. A hazard zone asdescribed herein may refer to an area in a warehouse in which it isallowable for pinch points to occur. Such an area may include warningsigns and may not permit pedestrian entry and accessibility.

Intersection of any polygon will result in the impingement distancebeing calculated and the intersection will be added to the list of datafor each intersection. Data for each intersection includes, but is notlimited to, the type of intersection, the intersection distance, theangle of intersection, and the distance along the path at which theintersection occurs. In embodiments, a pinch point as referenced hereinrefers to a location in a warehouse where any physical part of thematerials handling vehicle 10 (e.g., one or more tugger and/or trailerportions) approaches within a specified clearance distance of anystationary physical object in a warehouse. The specified clearancedistance may be, for example, 0.5 meters. Such clearance distances arerepresentative of a location clearance to permit pedestrianaccessibility, for example.

Referring now to FIG. 8, the path validation tool calculates the steerwheel velocity V_(S) and steering angle θ_(S) of the materials handlingvehicle 10 to dictate the linear velocity V_(A) (Eq. 1) and rotationalvelocity ω_(A) (Eq. 2) of the materials handling vehicle 10.

$\begin{matrix}{V_{A} = {{V_{S} \cdot \cos}\;\theta_{s}}} & {{Eq}.\mspace{14mu} 1} \\{\omega_{A} = \frac{{V_{S} \cdot \sin}\;\theta_{s}}{wheelbase}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

These velocities of the materials handling vehicle 10 are used todetermine the subsequent trailer's 50 (i.e., the first trailer 50coupled to the materials handling vehicle 10) linear V_(B) (Eq. 3) androtational ω_(B) (Eq. 4) velocities. Each trailer's linear V_(B) androtational ω_(B) velocities are used to determine those of thesubsequent trailer 50 (i.e, second, third, etc.) by the same method.

$\begin{matrix}{V_{B} = {{{V_{A} \cdot \cos}\;\theta_{hitchB}} - {{\omega_{A} \cdot D_{rearHitchA} \cdot \sin}\;\theta_{hitchB}}}} & {{Eq}.\mspace{14mu} 3} \\{\omega_{B} = {{- \frac{{V_{A} \cdot \sin}\;\theta_{hitchB}}{D_{frontHitchB}}} - \frac{{\omega_{A} \cdot \cos}\;{\theta_{hitchB} \cdot D_{rearHitchA}}}{D_{frontHitchB}}}} & {{Eq}.\mspace{14mu} 4}\end{matrix}$

Referring now to FIG. 9, steered trailers 50 are modeled as a set of twobasic trailers (e.g., trailer 50 shown in FIG. 8), where the first‘trailer’ is modeled using the characteristics of a front hitch bar 51that has the rear hitch distance set to zero, and the ‘second’ traileris modeled as a basic trailer as shown and described above in relationto FIG. 8. A steered trailer is modelled as two basic trailers in a row,with the first trailer having a wheelbase of zero.

FIG. 10 depicts a another embodiment of the path validation tool where,instead of using linear and rotational velocities to model the materialshandling vehicle and/or trailers along a path, the change in distanceand heading along the path are used. Further calculations would nolonger include the integration by time step. This could be considered asdividing the pose changes by one second to get speeds, then integratingover one second to get the same pose changes.

Integrating the materials handling vehicle 10 velocities gives the poseof the materials handling vehicle 10 at each time step. Integrating therotational velocity of each trailer 50 relative to the prior one givesthe relative angle of each trailer 50. It should be noted, for steeredtrailers, that they are modeled as two trailers as discussed above.θ_(hitchB)=θ_(hitchB) +t _(s)(ω_(B)−ω_(A))  Eq. 5θ_(hitchC)=θ_(hitchC) +t _(s)(ω_(C)−ω_(B))  Eq. 6

These angles are sufficient to fully define the trailer poses by workingbackward from the materials handling vehicle pose at each time step.Still referring to FIG. 10, the state is defined by the pose (x, y, θ)of A, and a list of relative angles. Given the trailer details (hitchlengths and wheelbase), B is calculated as:

$\begin{matrix}{{Hitch}\left\{ \begin{matrix}{B_{x} = {A_{x} - {{D_{rearHitchA} \cdot \cos}\; A_{\theta}} - {D_{frontHitchB} \cdot {\cos\left( {A_{\theta} + \theta_{hitchB}} \right)}}}} \\{B_{y} = {A_{y} - {{D_{rearHitchA} \cdot \sin}\; A_{\theta}} - {D_{frontHitchB} \cdot {\sin\left( {A_{\theta} + \theta_{hitchB}} \right)}}}} \\{B_{\theta} = {A_{\theta} + \theta_{hitchB}}}\end{matrix} \right.} & {{Eq}.\mspace{14mu} 7} \\{\mspace{79mu}{{Trailer}\left\{ \begin{matrix}{C_{x} = {B_{x} - {{wheelbase} \cdot {\cos\left( {B_{\theta} + \theta_{hitchC}} \right)}}}} \\{C_{y} = {B_{y} - {{wheelbase} \cdot {\sin\left( {B_{\theta} + \theta_{hitchC}} \right)}}}} \\{C_{\theta} = {B_{\theta} + \theta_{hitchC}}}\end{matrix} \right.}} & {{Eq}.\mspace{14mu} 8}\end{matrix}$

All subsequent poses are then calculated in order as discussed above.

FIG. 11 generally depicts one embodiment of a path validation tool toverify the operation of a materials handling vehicle along a path in awarehouse. The path validation tool generally comprises environmentallayout data of the warehouse, a proposed path within the warehouse andcorresponding to the environmental layout data, data on the materialshandling vehicle to include exterior dimensions, turning radius, if oneor more trailers are part of the vehicle, data on each trailer, obstacledata within the warehouse, and the like. The path validation tool willoverlay a clearance space around the external dimensions of thematerials handling vehicle, including trailers, and evaluate whether theclearance space intersects with obstacles in the warehouse, pointing outpinch points and collisions. It will also overlay collisions betweenvarious moving parts of the materials handling vehicle (e.g., one ormore trailers and tugger). The path validation tool can either highlightproblem areas with the configuration of the materials handling vehicleor with the proposed path in the warehouse. Thus, the path validationtool may execute path validation logic to identify the degree ofpotential impingement at the candidate positions as one or more problemareas of at least one of the proposed travel path and a configuration ofthe materials handling vehicle with respect to the proposed travel path.An existing path (taught or created) can be verified by the pathvalidation tool before implementation in the warehouse by, for example,automated guided vehicles (AGV). Various embodiments of the pathvalidation tool and the operation of the path validation tool aredescribed in detail herein.

For example, referring to FIG. 11, the calculated intersections by thepath validation tool are shown in relation to the movement of thematerials handling vehicle 10 and, if used, one or more trailers 50 inthe warehouse 40. FIG. 11 depicts a first position 33 and a secondposition 34 of a materials handling vehicle 10 and one or more trailers30 around a turning point 35 along a path 37 in a warehouse 40. Thefirst position 33 and the second position 34 are positions along thepath 37 before and after the turning point 35, respectively. The pathvalidation tool is used to validate paths in a warehouse, such as, forexample, the warehouse 40, and ensure the clearance polygons of thematerials handling vehicle 10 and trailers 50 will not be crossed andpinch points will not occur between the materials handling vehicle 10and trailers 50 and/or between trailers 50, and report where such casesdo occur. It is contemplated that the paths may be modified to overcomeany identified issues with the path by the path validation tool. Pinchpoints are locations within the warehouse where the materials handlingvehicle (e.g., one or more trailers and/or the two vehicles) approachwithin a defined distance of a structure, equipment, or an obstacle. Thedefined distance may be, for example and not by way of limitation, 0.5meters. Hazard zones are areas within the warehouse where pinch pointsare located. The path validation tool may use hazard zones defined in awarehouse map to disregard reporting of clearance impingements thatoccur in those areas. Further, the path validation tool may definematerials handling vehicle velocity, turning radius, etc. for one ormore zones to maintain clearance and prevent collisions in those one ormore zones.

The environmental data 255 (FIG. 3) and configuration data 250 (FIG. 3)are populated and used by the path validation tool to represent theoperational conditions of the materials handling vehicle 10 and one ormore trailers 50, if used, in the warehouse 40.

The aforementioned dynamic exterior and clearance boundaries 13, 19 ofthe materials handling vehicle 10, including trailers 50, may berepresented in Cartesian coordinates relative to the vehicle's kinematiccenter. These boundaries have a steering range within which they areactive. The steering range is defined by the minimum and maximumsteering angles of the materials handling vehicle 10, including anytrailers 50. It is contemplated that the aforementioned dynamic exteriorand clearance boundaries 13, 19 will change based on vehicle speed andsteering angle. In addition, the respective shapes of the exterior andclearance boundaries 13, 19 may change as the materials handling vehicle10, including any trailers 50, progress along the path, particularlywhere collisions are more likely to occur.

It is contemplated that, in some embodiments, there will be a minimumdistance d by which the dynamic exterior boundary 13 will be offset fromthe physical periphery of the vehicle for all steering angles of thematerials handling vehicle 10, including any trailers 50. In otherembodiments, there will be a minimum speed scan field represented by theexterior and clearance boundaries 13, 19 and this minimum scan fieldwill be required regardless of the steer angle. The materials handlingvehicle 10, including any trailers 50, will slow down as it/theyapproach obstacles. In which case, higher vehicle speeds need not beconsidered, and the minimum speed scan field would be the limitingfactor in vehicle travel planning. In most cases, it will beadvantageous to ensure that the dynamic exterior boundary 13 isconfigured to match the operational parameters of the particularmaterials handling vehicle in use for optimum operation of the pathvalidation tool of the present disclosure.

A path is an ordered collection of path segments consisting of straight,arc, and clothoid types. The path may be created or received in the pathvalidation tool and/or it may be derived from data taken from sensors ona materials handling vehicle driven along the path in the warehouse. Forexample, and not by way of limitation, the localization system of thematerials handling vehicle may be used to track the progress of amaterials handling vehicle that is manually driven through the warehouseand the subsequent data is loaded into the path validation tool.

Obstacles are defined in absolute warehouse Cartesian coordinates. Theyare point obstacles that may be flagged as fixed infrastructure (i.e.cannot be deleted from the quadtree). The path validation tool may alsoaccept a simultaneous location and mapping (SLAM) log data, data fromenvironment laser scans, and will use the resulting path to insertobstacles by repeatedly applying the described single laser scan method.For example, and not by way of limitation, laser scan data will bepassed into path validation tool, along with laser scanner parameterdata, which will generate obstacles that are inserted into the quadtree. Any unobserved obstacle will be deleted when a laser scan shouldhave, but fails to, detect it. This deals with pedestrians and vehiclesthat enter the laser scan range and then leave.

In the case where a path is defined, the velocities are not availableand the motion is a series of direct changes in pose. The calculationsare the same except distances are used instead of velocities and theintegration time step is set to one. Smaller distance steps will resultin better fidelity of the trailer paths.

It is contemplated that the path may be modified through use ofsegments. The calling function may get results for modified paths fasterif it splits the nominal path into shorter lengths. This would preventrecalculation of earlier unchanging segments as the end of the path isdetermined. Each of these segments should have all alternatives andtheir results stored, as the apparent best segment may not be the bestif it leads to problems further along the path. The number of pinchpoints for the entire path should be minimized. Additionally, checking ashorter section of path would give quicker iterations. The sectionsshould not be split near a turn, or perhaps splits should beconcentrated at turns. In any case, the path validation tool may, insome cases, need to backtrack quite a distance to deal with long trailertrains. The path validation tool should be able to be set to exit earlyif there is a collision at any point. In this case it is still importantto complete analysis of pinching paths, as that could be the optimalpath and a hazard zone is necessary.

It is contemplated that one or more inputs for the path validation toolare, but not limited to: a tugger type, a scan field set, a trailertype, a quantity of trailers, initial (starting) angles of the trailers,an AGV path, and/or a list of obstacles. It is contemplated that one ormore outputs for the path validation tool are, but not limited to: adetermination of: whether any intrusion field, or any part of the tuggerand trailer(s), will intersect any obstacle; whether any part of thetugger and trailer(s) will approach within pinch point distance of anyobstacle; the maximum steering angle of the tugger, or any trailer, isexceeded at any distance along the path; if any of the tugger andtrailers intersect each other; and for each obstacle impinging on thepinch point clearance, report the distance along the path and theimpingement distance; and show resultant hazard zones.

FIG. 12 details through a process 1000 one or more steps 1001-1005 toverify the path using the path validation tool. It is noted that, whilethe functions are enumerated and depicted as being performed in aparticular sequence in the depicted embodiment, the functions can beperformed in an alternative order without departing from the scope ofthe present disclosure. It is furthermore noted that one or more of thefunctions can be omitted without departing from the scope of theembodiments described herein.

As shown in FIG. 12, to verify the path of one or more vehicles usingthe path validation tools, a user may first enter details about the oneor more materials handling vehicles, such as, for example, hitch lengthor wheel base or other appropriate details as shown in block 1001. Next,the user may enter details regarding the appropriate exterior dimensionsas shown in block 1002. Optionally, the user may enter details about thewarehouse site or industrial site as shown in block 1003. As shown inblock 1004, the desired path may be driven and laser data may berecorded during the drive. In block 1005, path verification runs on thelogged data and results are output to one or more screens.

In embodiments, and as described above with respect to FIGS. 1-2, amaterials handling vehicle 10 may include a vehicle body 11, materialshandling hardware 15, one or more wheels 16, a drive unit D, a steeringunit S, a localization module L, a navigation module N, and a pathvalidation tool P, such that the drive unit D, steering unit S,localization module L, and navigation module N cooperate to direct thematerials handling vehicle 10 along a travel path 37 (FIG. 11) in awarehouse 40.

In an embodiment, and referring to a process 1300 of FIG. 13, the pathvalidation tool P includes environmental layout data of the warehouse, aproposed travel path within the warehouse, kinematics of the materialshandling vehicle 10, and a dynamic vehicle boundary of the materialshandling vehicle 10. The process 1300 starts path validation at block1302.

A method of executing path validation logic may include receiving aplurality of inputs into the path validation tool P. One or more inputs1304-1310 are received by the path validation tool P. For example, theone or more inputs include environmental layout data as an input 1304, aproposed travel path as an input 1306, a dynamic vehicle boundary as aninput 1308, and vehicle kinematics in as an input 1310. In embodiments,the kinematics of the material handling vehicle 10 include at least thekinematic center C of the materials handling vehicle 10, and data on thematerials handling vehicle 10 to include exterior dimensions, a turningradius, and pose data. The materials handling vehicle 10 may include atugger 20 and one or more trailers 50 coupled to the tugger 20, and thepose data may be indicative of pose data respectively of the tugger 20and the one or more trailers 50. Further, the dynamic vehicle boundaryof the materials handling vehicle 10 may approximate the physicalperiphery of the materials handling vehicle 10.

The method may further include determining vehicle pose as, for example,the path validation tool P executes path validation logic to, in block1312, determine vehicle pose along the proposed travel path. The methodmay include updating the dynamic vehicle boundary. For example, thelogic may further be executed to update the dynamic vehicle boundary inblock 1324 to account for changes in vehicle speed received as an input1320 and changes in steering angle received as an input 1322. The logicmay be executed to determine, in block 1314, whether the dynamic vehicleboundary of the vehicle is likely to intersect obstacles represented inthe environmental layout data based on the determined vehicle pose atcandidate positions along the proposed travel path. The logic may thenbe further executed to determine a degree of potential impingement atthe candidate positions by referring to the dynamic vehicle boundary ofthe materials handling vehicle and obstacle data represented in theenvironmental layout data. In embodiments, a degree of potentialimpingement includes an impingement distance that is an overlap distancebetween a potentially intersecting candidate and the dynamic exteriorboundary 13. Further, the materials handling vehicle 10 may include atugger 20 and one or more trailers 50 coupled to the tugger 20, and thepotentially intersecting candidate is one of the tugger 20, a trailer50, and an obstacle 52 represented by obstacle data in the environmentallayout data. For example, the potentially intersecting candidate may bea trailer 50. The overlap distance may be defined between the trailer 50and the dynamic exterior boundary 13 of the tugger 20 of the materialshandling vehicle 10. Alternatively, the overlap distance may be definedbetween the trailer 50 and the dynamic exterior boundary 13 of anothertrailer 50 of the one or more trailers 50 of the materials handlingvehicle 10. In another embodiment, the potentially intersectingcandidate is the obstacle 52, and the overlap distance is definedbetween the obstacle 52 and the dynamic exterior boundary 13 of thematerials handling vehicle 10.

In block 1316, the logic may be executed to modify the proposed travelpath to mitigate the degree of potential impingement. In block 1318, thedrive unit D, the steering unit S, the localization module L, and thenavigation module N cooperate to direct the materials handling vehicle10 along the modified proposed travel path. The method may furtherinclude navigating the materials handling vehicle 10 along the modifiedproposed travel path through cooperation of the drive unit, steeringunit, localization module, and navigation module.

In embodiments, the dynamic vehicle boundary of the path validation toolmay include a dynamic exterior boundary 13 of the materials handlingvehicle 10 and a dynamic clearance boundary 19 of the materials handlingvehicle 10. Referring to FIGS. 1B-1C, the dynamic clearance boundary 19is enlarged relative to at least a portion of the dynamic exteriorboundary 13 of the materials handling vehicle 10 to define an enlargedboundary about at least a portion of the materials handling vehicle 10.The path validation tool P may execute path validation logic todetermine in block 1314 whether the dynamic clearance boundary 19 of thematerials handling vehicle 10 is likely to intersect obstaclesrepresented in the environmental layout data based on the determinedvehicle pose at candidate positions along the proposed travel path. Thelogic may be further executed to correlate likely points of intersectionalong the proposed travel path with vehicle pose at the candidatepositions along the proposed travel path to build a list of potentiallyintersecting candidates along the proposed travel path, and to determinethe degree of potential impingement at the candidate positions byreferring to the list of potentially intersecting candidates, thedynamic exterior boundary 13 of the materials handling vehicle 10, andobstacle data represented in the environmental layout data of input1304.

In an embodiment, and referring to a process 1400 of FIG. 14, the pathvalidation tool P includes environmental layout data of the warehouse, aproposed travel path within the warehouse, kinematics of the materialshandling vehicle 10, and a dynamic exterior boundary 13 of the materialshandling vehicle 10, and a dynamic clearance boundary 19 of thematerials handling vehicle 10. The dynamic exterior boundary 13 of thematerials handling vehicle 10 approximates the physical periphery of thematerials handling vehicle 10. The dynamic clearance boundary 19 isenlarged relative to at least a portion of the dynamic exterior boundary13 of the materials handling vehicle 10 to define an enlarged boundaryabout at least a portion of the materials handling vehicle 10.

The process 1400 starts path validation at block 1402. One or moreinputs 1404-1410 are received by the path validation tool P. Forexample, the one or more inputs include environmental layout data inblock 1404, a proposed travel path in block 1406, a dynamic clearanceboundary 19 as an input 1409, a dynamic exterior boundary 13 as an input1408, and vehicle kinematics as an input 1410. The path validation toolP may execute path validation logic to determine vehicle pose along theproposed travel path in block 1412. In block 1414, the logic may beexecuted to determine whether the dynamic clearance boundary 19 of thematerials handling vehicle 10 is likely to intersect obstaclesrepresented in the environmental layout data based on the determinedvehicle pose at candidate positions along the proposed travel path.Thus, a method of executing path validation logic may includecorrelating likely points of intersection along the proposed travel pathwith vehicle pose at the candidate positions along the proposed travelpath to build a list of potentially intersecting candidates along theproposed travel path through the path validation tool.

For example, in block 1416, a list of intersecting candidates is built.For example, the logic may be executed to correlate likely points ofintersection along the proposed travel path with vehicle pose at thecandidate positions along the proposed travel path to build a list ofpotentially intersecting candidates along the proposed travel path. Inblock 1418, a degree of potential impingement at the candidate positionsis determined by referring to the list of potentially intersectingcandidates, the dynamic exterior boundary 13 of the materials handlingvehicle 10, and obstacle data represented in the environmental layoutdata. In block 1420, the proposed travel path is modified to mitigatethe degree of potential impingement. In block 1422, the drive unit D,steering unit S, localization module L, and navigation module Ncooperate to direct and navigate the materials handling vehicle 10 alongthe modified proposed travel path. The method may further includenavigating the materials handling vehicle 10 along the modified proposedtravel path through cooperation of the drive unit, steering unit,localization module, and navigation module.

In embodiments, and as described in greater detail below with respect toFIGS. 15-18, after receiving errors and modifying a proposed travel pathto address the errors through a path verification step, the pathvalidation tool may further comprise a path optimization tool thatdynamically alters, optimizes, and reduces errors with respect to amaterials handling vehicle's navigated travel path. For example, theproposed travel path may be set as the nominal travel path that amaterials handling vehicle navigates. The path optimization tool isconfigured to dynamically modify a nominal travel path during navigationof the materials handling vehicle based on path segment error reduction.As the materials handling vehicle navigates along the nominal travelpath, the path optimization tool may modify the nominal travel pathbased on detection of an obstacle. The materials handling vehicle maythen be directed onto a translated, modified travel path merging fromand to the nominal path to avoid the obstacle.

Referring now to FIGS. 15 and 16, it is contemplated that a materialshandling vehicle (i.e., a tow vehicle and any number of trailers),traveling in autonomous mode, should maintain a clearance distance fromall obstacles, not trigger laser fields on known obstacles, and notcause tow trailers to collide with one another or with known obstacles.The materials handling vehicle will be given a nominal path asillustrated in FIG. 16 for travel in autonomous mode. Obstacles (such asone of obstacle(s) 52 in FIG. 16) may be identified and added to anobstacle map while the materials handling vehicle follows the nominalpath. The obstacle map may also contain fixed infrastructure. In oneembodiment, the obstacle map is regularly updated by laser scans fromthe laser scanner of the materials handling vehicle. In one embodiment,the obstacle map is on a network and is updated by the laser scans ofnot only the materials handling vehicle, but other materials handlingvehicles operating in the warehouse. The nominal path may need to bealtered dynamically such that the tugger and trailers autonomouslycontinue around any identified obstacles, while following therequirements described earlier in this section. Any obstacle that is notdetected in a subsequent scans of that area will be removed from themap, as would happen when an obstacle has moved, potentially allowingthe nominal path to continue through that space without alteration.

Where obstacles in the obstacle map will impinge on the movement areaand/or the clearance area or clearance field geometry of the materialshandling vehicle, a modified path will be created based on translatingthe obstructed section of the nominal path to avoid the obstacle, asshown in FIG. 16. If this is not possible, due to other obstacles orinfrastructure being in the way, then the path optimization tool willtry to again however for the second try, the path optimization tool willnot consider the clearance area and will attempt to operate thematerials handling vehicle as if driving in a hazard zone. A hazard zoneis a marked area of the warehouse where the autonomous vehicle speed isrestricted. If a translated path is still not created, then thematerials handling vehicle will halt and wait for manual intervention.

In embodiments, for example, after modifying the proposed travel path inblock 1316 of FIG. 13, the path validation tool P may dynamically modifythe proposed travel path to establish a dynamically modified travelpath. The path validation tool P executes path validation logic todetermine vehicle pose along the modified proposed travel path as thedrive unit, steering unit, localization module, and navigation modulecooperate to direct the materials handling vehicle 10 along the modifiedproposed travel path, and determine whether the dynamic vehicle boundaryof the materials handling vehicle 10 is likely to intersect obstaclesrepresented in the environmental layout data based on the determinedvehicle pose at candidate positions along the modified proposed travelpath. The path validation tool further executes path validation logic todetermine a degree of potential impingement at the candidate positionsby referring to the dynamic vehicle boundary of the materials handlingvehicle 10 and obstacle data represented in the environmental layoutdata, dynamically modify the modified proposed travel path to mitigatethe degree of potential impingement and establish a dynamically modifiedtravel path configured to merge from and to the modified proposed travelpath, and navigate the materials handling vehicle 10 along thedynamically modified travel path.

If there is a potential translation required to avoid an obstacle, thena modified path (as illustrated in FIG. 16) will be created by combiningmerging paths from the nominal path (or current materials handlingvehicle location) to the translated path section, then another mergingpath back from the translated path section to the nominal path. Both the‘from’ and the ‘to’ merges are obtained by fitting a joining path, forexample a joining path could consist of a series of three clothoids. Themerge path lengths are varied until a close fit is found. For the tripleclothoid joining case, the fitter works by optimizing towards the lowestjoin error starting with a 1:1:1 length ratio for the ratios of clothoidlengths, the total length, and the curvature at the end of the firstclothoid. The initial total length is the Euclidean distance between thejoin points and curvature options are an even spread between the maximumallowed positive and maximum negative path curvature (essentially steerangle limits). Thus, in embodiments, establishment of the dynamicallymodified travel path configured to merge from and to the modifiedproposed travel path may include fitting a joining path to the modifiedproposed travel path, the joining path comprising a series of threeclothoids and merge path lengths, the merge path lengths configured tobe varied until a close fit comprising a lowest join error isdetermined. Optimization towards the lowest join error may include aninitial proposed merge path starting at a 1:1:1 length ratio withrespect to the ratios of clothoid lengths, the total length of theinitial proposed merge path, and a curvature at an end of a firstclothoid. The total length of the proposed merge path may include aEuclidean distance between a pair of join points, and curvature optionswith respect to the curvature may include an even spread between amaximum allowed positive curvature and a maximum negative pathcurvature. The even spread may be based on one or more steer anglelimits.

This replanning may occur as often as necessary. For example, as thematerials handling vehicle drives around an obstacle and revealsadditional obstacles that are added to the obstacle map, the existingmodified path may become obstructed and so be replanned. The vehicle maybe configured to only generate a modified path that is observed to befree of obstacles all the way to the return to the original path. Thevehicle may also be configured to generate a modified path where thereturn to the original path is not fully observed, in which case thevehicle may generate further modified path(s) to avoid subsequentlyrevealed obstacles as it progresses along the modified. If there is everno valid modified path back on to the nominal path, based on the currentobstacle map data, then the materials handling vehicle will halt andawait manual intervention.

In one embodiment, a path verification step as applied by the pathvalidation tool will return errors in the nominal path and the locationalong the nominal path where each error occurs. The path optimizationtool will attempt to reduce each error as much as possible by graduallyadjusting the nominal path leading up to the distance at which the erroroccurs. Adjustments include changing the length of each path segment andadding path segments. The path segments may be smoothly joined, with amaximum allowed curvature and being within allowable sharpness limits.The path optimization tool will identify any location where the lowesterror causes a pinch point. Nearby pinch points may be combined into asingle zone. These pinch points are highlighted for a user to see andacknowledge, except for those pinch points that are within an existinghazard zone on the warehouse map.

If the nominal path is derived from a user manually driving thematerials handling vehicle in a warehouse, the resulting manual path mayappear as a series of shallow arcs and clothoids. The path optimizationtool will smooth these series of shallow arcs and clothoids such thatthe final nominal path comprises straight segment where straight linepaths are desired and smooth, continuous curves where turns are desired.

In this embodiment, the path optimization tool will provide an outputcomprising an error vector, type, and distance at which the erroroccurs. If the error is a collision type (i.e., intersection between thedynamic boundary and an obstacle), then a translated path will be foundthat avoids the obstacle, or the tool will return an optimizationfailure if such a translated path cannot be found. If the error is apinch type (i.e., intersection between the dynamic clearance area and anobstacle), then a translated path will be found, or the tool will recorda pinch point at the point of the error along the nominal path if such atranslated path cannot be found.

The path optimization tool will recursively apply corrections oralternative translated paths until a valid translated path is found. Thepath optimization tool will try to enforce convergence by allowingchanges in the path divergence (distance between the translated path andthe nominal path along the travel direction) up to a maximum pathdivergence threshold. The path optimization tool will also use a maximumiteration threshold for pinch point avoidance planning as it may beimpossible to avoid pinch points in tight locations.

At the first path distance at which an intersection with an obstacleoccurs, the path optimization tool will determine if the current pose ofthe materials handling vehicle can be moved away from the obstacle toavoid the intersection without causing additional intersections with thesame or other obstacles. If possible, create the translated path andsmooth the translated path. The path optimization tool will smooth thetranslated path by identifying the minimal amount of change in thetranslated path to achieve a desired final pose. Generally this will belengthening or shortening the path segments of the translated path orchanging the sharpness (change in curvature of the translated path). Insome embodiments, it may be necessary to add segments to the translatedpath to smooth it. The path smoothing will attempt to leave the nominalpath earlier then rejoin the nominal path farther on, so as not to alterthe nominal path with the translated path. The path optimization toolwill attempt to verify the translated path again and check whether theintersection distance is before or after the last one. If it is before,then the path optimization tool will recursive correct the translatedpath. The path optimization tool will use a recursive correctionthreshold to halt created the translated path because it may not bepossible to avoid pinching in some locations.

Along with the nominal path, a swept outline is used to identify thepaths of the one or more trailers following the tow vehicle along thenominal path. The shape of the swept outline of the materials handlingvehicle may change due to the additions of translated paths. Simplyextending a straight segment of the nominal path with a translated pathshould not change the shape of the swept outline which makes translatedpaths easier to predict. Changing an arc length of a nominal path with atranslated path may cause a discrepancy in the swept outline andchanging a curvature of a nominal path with a translated path may causea larger discrepancy. If the discrepancies vary too greatly between pathadjustments then smaller adjustments would be necessary to allowconvergence.

In another embodiment, and referring to FIG. 17, the path verificationstep, as illustrates through blocks 101-104 of FIG. 17, will returnerrors in the nominal path (i.e., locations where the nominal pathintersects with known obstacles) and the location along the nominal paththe error occurs. The path optimization tool will locate contiguoussegments (i.e. a section of path from a start to an end distance) inblock 105 that have an error of the same type. The path optimizationtool will select the first occurring error regardless of type however,if there are multiple errors along the nominal path, the pathoptimization tool will prioritize them in order of: maximum steerexceeded in block 106; self collision (i.e., between trailers and/orbetween trailers and the tow vehicle) in block 107; intersection with anobstacle indicating collision in block 108; and lastly any pinch pointerrors in block 109. The cases of maximum steer-exceeded andself-collision in blocks 106-107 are likely caused by too severe of aturn at an earlier point in the nominal path. In block 110, the offsetof the affected trailer connection from the tow vehicle is used to shiftthe affected nominal path region backward. The severe part is graduallysmoothed out in block 113 to have a smaller curvature. This isiterative, until the steer-exceeded or self-collision warning does notoccur and the path is verified in block 114 and the issue solved inblock 112. For the collision and pinch point cases, the combined seriesof swept outlines will be transformed minimally in blocks 111-121 suchthat there are no collisions or pinch points. If pinch points cannot beavoided in block 115 then the path optimization tool will attempt tokeep one side of the affect trailer not pinched and move on. If pinchpoints on both sides of the affected trailer cannot be avoided then keepthe impingement distance on each side equidistant. For example, in block124, a hazard zone in such a scenario may be marked. Collisions must beavoided, however, as determined in block 123, and failure to do so willresult in block 122 in a “no path possible” result by the pathoptimization tool.

After any change is made to the nominal path, the translated paths needsto be merged into the nominal path and verified for operation of thematerials handling vehicle. The path merges themselves could result inadditional verification failures. Multiple translated paths for eacherror may be tried and a variety of merge distances will be attempteduntil a good merge between the translated path and nominal path isfound. The exit merge will undergo the same treatment but it isacceptable that the exit merge has errors. A bad exit merge would resultin subsequent path alterations. If an attempted change does not work,different transforms of the translated path will be attempted. A slightrotation of the translated path could be enough to pass the checks.

A contiguous distance refers to a range of distances along a path, froma start distance to an end distance, in which similar obstructions(s)occur in close proximity to one another.

To attempt the transformation, a path segment is separated from thepath, creating a start path, a middle path, and an end path. The middlepath is then transformed such that the obstacles are all avoided. Fromthe transformation, there are two joins necessary; start to middle andmiddle to end. A join starts at a point before the end of the first pathand ends at a point after the start of the second path. The distancereplaced on the paths will vary depending on how much discontinuity hasbeen introduced by the transform. Variations of the transformation willbe attempted until an unobstructed path is obtained.

A function may exist that joins two arbitrary poses in as direct amanner as possible without exceeding the maximum curvature limits or themaximum sharpness limits. The joiner is a series of three clothoids,though other types of joiner are possible. The path optimization toolmay plan many valid joiners and choose the best one, which is defined asthe first joiner planned that has error within the configurable jointolerance. Also, in one implementation, the first result is the shortestjoiner due to joiner length being increased for each subsequentoptimization step.

To identify the proper clothoids, we use the following data:curvature_start value, curvature_end value, angle-change value,maximum-curvature value, maximum-sharpness value, minimum-sharpnessvalue, and an initial-length estimate. From that data, the length ofeach segment and the intermediate curvature(s) can be optimized toidentify the best fit triple clothoid. The calculations are constrainedsuch that the solution is found once the end pose (x, y, and θ) isbrought within preconfigured tolerances of the target (e.g., onecentimeter and one degree).

Once a joiner is found, the path verification step may be run by thepath optimization tool to ensure that the original issue of anintersection with an object is fixed and no new issue was added. Ifthere is still a problem, potentially altering the join distance may beall that is needed to solve the issue. It is contemplated that a largerjoin distance may result in a smoother transition. That is, the pathoptimization tool may start far back on the nominal path and workforward, but try to always end on the start of the translated path toensure a consistent swept area. Thus, the path verification step may berun on the path each time it is modified by a candidate joiner. Further,the path distance at which the joiner starts or ends may be varied untila suitable or best joiner is found.

FIG. 18 graphically depicts changes to and from the nominal path. Thefirst graph shows a top down view where the nominal path has beenmodified. The translated path section has been moved slightly upwardsand left of the nominal. The two joiners have been fitted to morph thenominal path smoothly to and from the translated path section. Thefollowing two graphs show the details of the three clothoids that makeup each joiner. Note that the curvature is continuous, which allows thematerials handling vehicle to follow the path smoothly and withoutneeding to stop to change the steer angle.

The path optimization tool may be used on a computer to verify a nominalpath in a warehouse and identify any problems with obstacles before anautomated vehicle following the path is commissioned and operated, or onan automated vehicle to dynamically modify the nominal path to avoid newobstacles identified by the laser scanner. It is contemplated that theautomated vehicle may hug an obstacle for a maximum length beforerejoinder with the nominal path is required. For all pinch pointsidentified, the path optimization tool may still allow an automatedvehicle to operate, as the vehicle controller may operate the automatedvehicle at a slower speed through the pinch zone with the pinch point.

The path optimization tool directly verifies the actual tow vehicle,trailer, and clearance field geometry will not collide with obstacles,rather than using approximations that could be suboptimal. The pathoptimization tool considers a train of trailers in addition to the towvehicle, whereas other approaches have so far only considered the AGVitself. The use of clothoid joiners rather than splines, and clothoidsare arguably smoother for a materials handling vehicle to follow thansplines. The path optimization tool enforces a continuous pathcurvature, a maximum path curvature, and a maximum path sharpness toensure that the translated path is physically able to be followed. Thepath optimization tool updates the obstacle map as new laser scan datais received and objects are identified, whereas some other approachesrequire full information up front. The path optimization tool may alsoconsider trailer paths behind a tow vehicle during obstacle avoidance.

Certain terminology is used in the disclosure for convenience only andis not limiting. Words like “left,” “right,” “front,” “back,” “upper,”“lower,” etc., designate directions in the drawings to which referenceis made. The terminology includes the words noted above as well asderivatives thereof and words of similar import.

It is also noted that recitations herein of “at least one” component,element, etc., should not be used to create an inference that thealternative use of the articles “a” or “an” should be limited to asingle component, element, etc.

It is noted that recitations herein of a component of the presentdisclosure being “configured” or “programmed” in a particular way, toembody a particular property, or to function in a particular manner, arestructural recitations, as opposed to recitations of intended use. Morespecifically, the references herein to the manner in which a componentis “configured” or “programmed” denotes an existing physical conditionof the component and, as such, is to be taken as a definite recitationof the structural characteristics of the component.

It is noted that terms like “preferably,” “commonly,” and “typically,”when utilized herein, are not utilized to limit the scope of the claimedinvention or to imply that certain features are critical, essential, oreven important to the structure or function of the claimed invention.Rather, these terms are merely intended to identify particular aspectsof an embodiment of the present disclosure or to emphasize alternativeor additional features that may or may not be utilized in a particularembodiment of the present disclosure.

For the purposes of describing and defining the present invention it isnoted that the terms “substantially” and “approximately” are utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. The terms “substantially” and “approximately” are alsoutilized herein to represent the degree by which a quantitativerepresentation may vary from a stated reference without resulting in achange in the basic function of the subject matter at issue.

While particular embodiments have been illustrated and described herein,it should be understood that various other changes and modifications maybe made without departing from the spirit and scope of the claimedsubject matter. Moreover, although various aspects of the claimedsubject matter have been described herein, such aspects need not beutilized in combination. It is therefore intended that the appendedclaims cover all such changes and modifications that are within thescope of the claimed subject matter.

It is noted that one or more of the following claims utilize the term“wherein” as a transitional phrase. For the purposes of defining thepresent invention, it is noted that this term is introduced in theclaims as an open-ended transitional phrase that is used to introduce arecitation of a series of characteristics of the structure and should beinterpreted in like manner as the more commonly used open-ended preambleterm “comprising.”

What is claimed is:
 1. A materials handling vehicle comprising a vehiclebody, materials handling hardware, one or more wheels, a drive unit, asteering unit, a localization module, a navigation module, and a pathvalidation tool, wherein: the drive unit, steering unit, localizationmodule, and navigation module cooperate to direct the materials handlingvehicle along a travel path in a warehouse; the path validation toolcomprises environmental layout data of the warehouse, a proposed travelpath within the warehouse, kinematics of the materials handling vehicle,and a dynamic vehicle boundary of the materials handling vehicle; thedynamic vehicle boundary of the materials handling vehicle approximatesa physical periphery of the materials handling vehicle and is defined atan offset distance from the physical periphery of the materials handlingvehicle; the path validation tool executes path validation logic to (i)determine vehicle pose along the proposed travel path, (ii) update thedynamic vehicle boundary to account for changes in vehicle speed andsteering angle to update the offset distance from the physical peripheryof the materials handling vehicle, (iii) determine whether the dynamicvehicle boundary of the vehicle is likely to intersect obstaclesrepresented in the environmental layout data based on the determinedvehicle pose at candidate positions along the proposed travel path, (iv)determine a degree of potential impingement at the candidate positionsby referring to the dynamic vehicle boundary of the materials handlingvehicle and obstacle data represented in the environmental layout data,and (v) modify the proposed travel path to mitigate the degree ofpotential impingement; and the drive unit, steering unit, localizationmodule, and navigation module cooperate to direct the materials handlingvehicle along the modified proposed travel path.
 2. The materialshandling vehicle of claim 1, wherein: the dynamic vehicle boundary ofthe path validation tool comprises a dynamic exterior boundary of thematerials handling vehicle and a dynamic clearance boundary of thematerials handling vehicle; the dynamic clearance boundary is enlargedrelative to at least a portion of the dynamic exterior boundary of thematerials handling vehicle to define an enlarged boundary about at leasta portion of the materials handling vehicle; and the path validationtool executes path validation logic to (i) determine whether the dynamicclearance boundary of the materials handling vehicle is likely tointersect obstacles represented in the environmental layout data basedon the determined vehicle pose at candidate positions along the proposedtravel path, (ii) correlate likely points of intersection along theproposed travel path with vehicle pose at the candidate positions alongthe proposed travel path to build a list of potentially intersectingcandidates along the proposed travel path, and (iii) determine thedegree of potential impingement at the candidate positions by referringto the list of potentially intersecting candidates, the dynamic exteriorboundary of the materials handling vehicle, and obstacle datarepresented in the environmental layout data.
 3. The materials handlingvehicle of claim 1, wherein the path validation tool executes path logicto determine vehicle pose along one of the proposed travel path and themodified proposed travel path at pre-determined intervals.
 4. Thematerials handling vehicle of claim 3, wherein the materials handlingvehicle comprises a tugger and one or more trailers coupled to thetugger, and the pose data is indicative of pose data respectively of thetugger and the one or more trailers.
 5. The materials handling vehicleof claim 1, wherein the kinematics of the materials handling vehiclecomprise at least a kinematic center C of the materials handlingvehicle, data on the materials handling vehicle to include exteriordimensions of the materials handling vehicle, a turning radius, and posedata.
 6. The materials handling vehicle of claim 1, wherein thematerials handling vehicle comprises a tugger and one or more trailerscoupled to the tugger, the dynamic vehicle boundary approximates aphysical periphery of the tugger of the materials handling vehicle, anda potentially intersecting obstacle is a trailer of the one or moretrailers coupled to the tugger.
 7. The materials handling vehicle ofclaim 1, wherein the materials handling vehicle comprises a tugger andone or more trailers coupled to the tugger, the dynamic vehicle boundaryapproximates a physical periphery of a trailer of the one or moretrailers of the materials handling vehicle, and a potentiallyintersecting obstacle is another trailer of the one or more trailerscoupled to the trailer.
 8. The materials handling vehicle of claim 1,wherein the materials handling vehicle comprises a tugger and one ormore trailers coupled to the tugger, the dynamic vehicle boundaryapproximates a physical periphery of one of the tugger and the one ormore trailers of the materials handling vehicle, and a potentiallyintersecting obstacle is an obstacle represented in the environmentallayout data separate from the materials handling vehicle.
 9. Thematerials handling vehicle of claim 1, wherein: the path validation toolexecutes path validation logic to (i) determine vehicle pose along themodified proposed travel path as the drive unit, steering unit,localization module, and navigation module cooperate to direct thematerials handling vehicle along the modified proposed travel path, (ii)determine whether the dynamic vehicle boundary of the materials handlingvehicle is likely to intersect obstacles represented in theenvironmental layout data based on the determined vehicle pose atcandidate positions along the modified proposed travel path, (iii)determine a degree of potential impingement at the candidate positionsby referring to the dynamic vehicle boundary of the materials handlingvehicle and obstacle data represented in the environmental layout data,(iv) dynamically modify the modified proposed travel path to mitigatethe degree of potential impingement and establish a dynamically modifiedtravel path configured to merge from and to the modified proposed travelpath; and (v) navigate the materials handling vehicle along thedynamically modified travel path.
 10. The materials handling vehicle ofclaim 9, wherein establishment of the dynamically modified travel pathconfigured to merge from and to the modified proposed travel pathcomprises fitting a joining path to the modified proposed travel path,the joining path comprising a series of three clothoids and merge pathlengths, the merge path lengths configured to be varied until a closefit comprising a lowest join error is determined.
 11. The materialshandling vehicle of claim 10, wherein optimization towards the lowestjoin error comprises an initial proposed merge path comprising a 1:1:1length ratio with respect to the ratios of clothoid lengths, the totallength of the initial proposed merge path, and a curvature at an end ofa first clothoid.
 12. The materials handling vehicle of claim 11,wherein the total length of the proposed merge path comprises aEuclidean distance between a pair of join points.
 13. The materialshandling vehicle of claim 11, wherein curvature options with respect tothe curvature comprise an even spread between a maximum allowed positivecurvature and a maximum negative path curvature, the even spread basedon one or more steer angle limits.
 14. The materials handling vehicle ofclaim 1, wherein the path validation tool executes path validation logicto identify the degree of potential impingement at the candidatepositions as one or more problem areas of at least one of the proposedtravel path and a configuration of the materials handling vehicle withrespect to the proposed travel path.
 15. The materials handling vehicleof claim 1, wherein a degree of potential impingement comprises animpingement distance that is an overlap distance at candidate positionsindicative of an overlap between the dynamic vehicle boundary of thematerials handling vehicle and obstacle data.
 16. A method of executingpath validation logic with respect to a materials handling vehiclecomprising a vehicle body, materials handling hardware, one or morewheels, a drive unit, a steering unit, a localization module, anavigation module, and a path validation tool, the drive unit, steeringunit, localization module, and navigation module cooperate to direct thematerials handling vehicle along a travel path in a warehouse, themethod comprising: receiving a plurality of inputs into the pathvalidation tool, the plurality of inputs comprising environmental layoutdata of the warehouse, a proposed travel path within the warehouse,kinematics of the materials handling vehicle, and a dynamic vehicleboundary of the materials handling vehicle that approximates a physicalperiphery of the materials handling vehicle and is defined at an offsetdistance from the physical periphery of the materials handling vehicle;determining vehicle pose along the proposed travel path through the pathvalidation tool; updating the dynamic vehicle boundary to account forchanges in vehicle speed and steering angle through the path validationtool to update the offset distance from the physical periphery of thematerials handling vehicle; determining whether the dynamic vehicleboundary of the vehicle is likely to intersect obstacles represented inthe environmental layout data based on the determined vehicle pose atcandidate positions along the proposed travel path through the pathvalidation tool; determining a degree of potential impingement at thecandidate positions by referring to the dynamic vehicle boundary of thematerials handling vehicle and obstacle data represented in theenvironmental layout data through the path validation tool; modifyingthe proposed travel path to mitigate the degree of potential impingementthrough the path validation tool; and navigating the materials handlingvehicle along the modified proposed travel path through cooperation ofthe drive unit, steering unit, localization module, and navigationmodule.